1,721,059 research outputs found
STARFISH SAPONINS .34. NOVEL STEROIDAL GLYCOSIDE SULFATES FROM THE STARFISH ASTERIAS-AMURENSIS
No full textA reinvestigation of the exts. from the starfish A. amurensis has led to the isolation of 8 novel steroidal glycosides along with major amts. of the already reported glycoside B2, ovarian asterosaponin-1, and ovarian asterosaponin-4. Four novel compds. are asterosaponins assigned as the asteroside A (I), B (II), C (III), and D (IV). Main differences among the novel asterosaponins reside in the steroid side chains. The 2nd group of saponins consists of 4 new polyhydroxysteroidal xylopyranosides, designated amurensosides A (V), B (VI), C (VII), and D (VIII)
Starfish Saponins .47. Steroidal Glycoside Sulfates and Polyhydroxysteroids From Aphelasterias-japonica
No full textTwo novel steroidal xyloside sulfates, aphelasterosides A {3} and B {5}, and two novel polyhydroxysteroids 2 and 7 have been isolated from the starfish Aphelasterias japonica. Their structures were elucidated mainly b spectroscopic methods
POLAR STEROIDS FROM THE MARINE SCALLOP PATINOPECTEN-YESSOENSIS
No full textEight polyhydroxylated sterols, 7 of them novel, were isolated from the hepatopancreas of the scallop P. yessoensis. Compds. I-VII possessed the same Δ7-3β,5α,6β-triol nucleus but differed in the side chains. One very minor component VIII had an addnl. OH group at C-9α. Their structures were deduced from 1H and 13C NMR and mass spectral data and by comparison with synthetic model compds
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Transient Ca2+-dependent activation of ERK1 and ERK2 in cytotoxic responses induced by maitotoxin in breast cancer cells
No full textTreatment of MCF-7 breast cancer cells with the marine toxin maitotoxin (MTX) induces cell death. The cytotoxic effects are clearly detectable within 2-4 h after cell treatment with 10(-10)-10(-9) M concentrations of MTX, The response was found to depend on extracellular Ca2+, inasmuch as cell death was prevented when culture dishes received MTX, following addition of EGTA, MTX caused transient phosphorylation of extracellular signal-regulated kinase isoforms 1 and 2 (ERK1 and ERK2) mitogen-activated protein kinase isoforms in MCF-7 cells, which was maximal 15 min after toxin addition to culture vessels. The effect,vas dependent on influx of extracellular Ca2+, as it was abolished by EGTA, and was induced by ionophores, such as A23187 and ionomycin, Our findings show that signaling pathways involving Ca2+ ions may cause activation of ERK1 and ERK2 in cell death responses
Oral and intraperitoneal acute toxicity studies of yessotoxin and homoyessotoxins in mice.
No full textThe acute toxicity of yessotoxin (YTX), homoyessotoxin (homoYTX) and 45-hydroxy-homoyessotoxin (45-OH-homoYTX) has been studied in comparison to that of okadaic acid (OA), the main diarrhogenic toxin, both after intraperitoneal (i.p.) and oral administration. After i.p. administration, homoYTX and YTX showed similar lethality (LD(50)=444 microg/kg and 512 microg/kg), higher than that of OA (LD(50)=225 microg/kg), while 750 microg/kg of 45-OH-homoYTX did not cause death. OA induced the already known toxic signs: before death, mice were motionless and cyanotic; small intestine and liver damage were shown at post-mortem. Mice treated with YTX and homoYTX were restless and jumped before death; necroscopy did not show major changes. After oral treatment, 2 mg/kg of OA induced diarrhoea and body weight loss, causing 4/5 deaths; necroscopy and/or histology revealed degenerative lesions to small intestine, forestomach and liver (confirmed by increased plasma transaminase), but no myocardium alterations. On the contrary, the oral treatment with YTX (1 and 2 mg/kg) and its derivatives (1 mg/kg) did not cause any death or signs of toxicity, except some ultrastructural myocardiocyte alterations, adjacent to capillaries, such as cytoplasmic protrusions (YTX, 1 and 2 mg/kg), fibrillar alteration (YTX, 1 mg/kg) or mitochondria assemblage (45-OH-homoYTX). Altogether, our data show that YTX and its derivatives are less toxic than OA after acute oral and i.p. treatments, at doses which may represent up to 100 times of the possible human daily intake
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